<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <div id="app">
        姓: <input type="text " v-model="xing"> </br>
        名: <input type="text " v-model="ming"> </br>
        姓名 <span>{{ xing.slice(0,3) }}-{{ming}}</span>
    </div>

    <script src="../JS/vue.js"></script>
    <script>
        new Vue({
            el: '#app',

            data() {
                return {
                    xing: '张',
                    ming: '三',
                }
            }
        })
    </script>
</body>

</html>